The present invention relates to a three-phase separator, wherein a feed comprising a gas phase and a lighter liquid and a heavier liquid phase is separated into the three phases gas, lighter liquid and heavier liquid. Such a separator is also called a gas/liquid/liquid separator. Three-phase separators are used in the oil industry to separate a mixture of hydrocarbonsxe2x80x94gas and oil, and water into the constituents gas, oil and water.
Examples of such separators are described in U.S. Pat. No. 3,469,373 and in the book xe2x80x98Surface Production Operations, Design of Oil-Handling Systems and Facilitiesxe2x80x99, volume 1, 2nd edition, K Arnold and M Stewart, Gulf Publishing Company, 1998 on page 135 and further.
A known three-phase separator comprises a normally horizontal vessel defining a liquid separation space and a gas space above the liquid separation space, which vessel has an inlet end space provided with a feed inlet and an outlet end space provided with separate outlets for the three phases, which vessel further comprises an inlet device in the form of an inlet diverter.
During normal operation a feed comprising a mixture of gas and liquids is introduced through the inlet into the vessel. The feed collides with the inlet diverter, and the sudden change of momentum causes a first separation of gas and liquids. Gas enters the gas space, and the liquids enter the liquid separation space where they are separated in a lighter liquid phase and a heavier liquid phase under the influence of gravity. Gas and the liquid phases are separately removed from the vessel through the outlets. The inlet diverter of the known three-phase separator is a vertical plate that extends into the liquid separation zone. In this way, the diverter forces the liquids to enter the liquid-filled liquid separation space.
A disadvantage of the known separator is a low separation capacity.
It is an object of the present invention to overcome this drawback.
To this end the three-phase separator according to the present invention comprises a normally horizontal vessel defining a liquid separation space and a gas space above the liquid separation space, which vessel has an inlet end space provided with a feed inlet and an outlet end space provided with separate outlets for the three phases, which vessel further comprises an inlet device comprising a primary separator which is arranged in the gas space and a tilted return tray arranged in the gas space under the primary separator having a lower end that is located near the inlet end wall of the vessel, such that a passage is defined between the lower end and the inlet end wall.
Applicants found that with the separator according to the invention a higher separation capacity can be achieved. Without wanting to be limited in any way by the following theory, applicants believe that the improved capacity is achieved because the liquid is guided to the liquid separation space via the inlet end wall of the separator. Because of this guiding of the liquid flow less turbulence in the liquid phase results as compared to the prior art devices. Because of the decrease in turbulence a more efficient settling of the liquid-liquid phases will result and hence an improved separation efficiency.